The present invention relates to a fuel injector.
German Published Patent Application No. 32 28 079 A1 describes a fuel injector having two valve needles with which it is capable of controlling multiple injection orifices individually. Each valve needle is pre-tensioned against a respective sealing seat by a spring. If one needle is raised out of its sealing seat by a certain clearance, it strikes against a stop of the other valve needle and takes the second valve needle with it as the travel progresses. The two sealing seats of the two valve needles close different injection orifices, which may be directed at differing angles. However, the construction is made up of multiple parts and two sealing seats must be manufactured to precise specifications, which gives rise to high costs.
German Published Patent Application No. 30 48 304 A1 describes a fuel injector for internal combustion engines having a valve needle and a secondary needle in a borehole in the valve needle. The portion of the valve needle which, near the combustion chamber is configured as a valve-closure member, cooperates with a valve seat surface to form a sealing seat that isolates injection orifices from the fuel inlet. The secondary needle which is guided in the valve needle also has a valve-closure member, which cooperates with a second valve seat surface of the fuel injector. The secondary needle is drawn towards the valve needle by a spring that is located in the valve needle, and it also forms a sealing seat against the valve needle with a valve seat surface in the valve needle. When the hydraulically actuated fuel injector begins to open as a result of rising pressure in the fuel supply line, the secondary needle is forced out of its sealing seat in the valve needle and towards the sealing seat in the valve body and closes a group of injection orifices, while another group of injection orifices is opened. If the pressure continues to rise, the valve needle is raised out of its sealing seat and after a certain travel takes the secondary needle with it, the secondary needle striking against a stop of the valve needle. All injection orifices are then opened. The disadvantage of this arrangement is that in all three sealing seats must be produced to exact specifications.
German Published Patent Application No. 31 20 044 C2 also describes a fuel injector having two valve needles, which may be used to open injection orifices in two groups. In this arrangement, one valve needle is disposed inside the other, which is constructed as a hollow valve needle. The valve needle which is designed as a hollow needle has injection orifices in its end near the combustion chamber. The disadvantage of this arrangement is that the production of the hollow needle is highly labor-intensive since it also has injection orifices, so that two functions, are combined in a single component, each requiring that the component be produced to a high degree of precision.
The fuel injector according to the present invention may have the advantage that it provides a solution for sequentially opening groups of injection orifices in a manner that may be inexpensive and easily manufacturable, since the additional group of injection orifices may not require an additional sealing seat manufactured with a high degree of precision in order to be able to open separately. For Example, the angle over which the fuel is distributed in the fuel injector""s jet pattern may be adjustable as a function of the valve lift.
A first circle of injection orifices may be covered by tongues in the disc spring. Further injection orifices may have different injection angles and may be offset with respect to one another by a circumferential angle. In such a case, initially when the injected volume and the load on the internal combustion engine are low, only a certain number of injection orifices having a narrow injection angle may be opened, so that a fuel injection jet may be formed that is made up of fuel jets from those injection orifices having an overall narrow injection angle. As the load on the combustion engine increases and the demand on the stratified charge operation of a combustion engine running according to the lean-burn concept rises correspondingly, the injection orifices of the additional orifice circle may also be opened. These may be arranged over a larger injection angle. The fuel injection jet that is injected overall may be delivered over a larger angle.
An example embodiment of the fuel injector according to the present invention is illustrated in simplified form in the drawings and is explained in greater detail in the following description.